1. Field of the Invention
The present invention relates to a rolling train for rolling girder sections. The rolling train includes at least one two-high reversing roughing stand and several subsequent universal stands for work rolling and finish rolling, wherein two universal stands and an upsetting stand are combined into a reversing tandem group.
2. Description of the Related Art
European Patent No. 02 56 409 discloses a section steel rolling mill with a two-high reversing roughing stand, and with a universal work stand and a flange upsetting stand combined to form a reversing tandem group, as well as with a universal finishing stand provided at the exit side. The section steel rolling mill illustrated in FIG. 1 of European Patent 02 56 409 provides for roughing in the two-high reversing roughing stand in 7 to 15 passes before the preformed girder is transferred to the reversing tandem stand group. By repeatedly rolling the preformed girder in 3 to 5 passes, the desired section is obtained approximately and, after the last pass and after the girder flanges have been rolled to the exact desired width, the girder is introduced into a finishing stand. The subsequent universal finishing pass rolls the girder into its final shape.
It is the intention in the European Patent 02 56 409 to improve this prior art which is referred to as being complicated and proposes to integrate the universal finishing stand into the reversing tandem stand group. Simultaneously, it is provided that, by an appropriate construction of the rolls of the universal work stand and the universal finishing stand, the girder section is alternatingly rolled into a H-shape and a X-shape, wherein the last pass is rolled in a H-shape. For this purpose, the vertical rolls of the universal work stand are constructed with a slight double-cone shape, while the universal finishing stand is equipped with cylindrical vertical rolls. In the prior art, this configuration of rolls and method of operation is mentioned as providing an advantageous kneading of the root portions of the flange.
This proposed arrangement of stands for carrying out the above-described rolling method on the rolling mill does reduce the investments required for the rolling mill as compared to known rolling mills because it omits a universal finishing stand and an upsetting stand. However, there is the simultaneous disadvantage that the universal finishing stand always participates in the deformation of the girder during the reversing passes in the reversing tandem group and, thus, is subject to the same wear as the universal work stand. Since the universal finishing stand is also utilized for the final finishing pass, the wear to be expected will make it necessary to exchange the rolls of this universal finishing stand frequently if a decrease in quality is unacceptable. Accordingly, the advantage achieved by the less complicated or expensive construction is eliminated because the costs saved by the omitted separate finishing stand and the corresponding upsetting stand are compensated by the additional costs for the rolls.